We have done preliminary characterization of mitochondrial DNAs isolated from three species of Drosophila. Electron microscope heteroduplex and restriction endonuclease analyses have revealed that these mtDNAs have undergone a significant evolutionary divergence in their nucleotide sequences. We are constructing specific cleavage maps of these mtDNAs using various restriction endonucleases. Restriction endonucleases recognize specific base sequences within a DNA molecule and have proven useful in mapping genes and detecting single base-pair substitutions. We have determined the levels of intra-specific variation in the restrictive maps of three species.